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Your Letters

Send your letters to The Editor, E&T, Michael Faraday House, Six Hills Way, Stevenage, Herts SG1 2AY, UK, or to engtechletters@theiet.org. We reserve the right to edit letters and to use submissions in any other format.

What price smart meters?

I agree with John Cowburn’s point (Letters, June 2014) about smart meters being too complicated in the UK and that they themselves do not save energy. Last year the Office of National Statistics announced that over the five-year period to 2011, consumers had cut back their home usage by 24.7 per cent. This has been prompted by escalating energy bills and so the work of saving energy has already been done by high prices.

I recently wrote to Baroness Verma, the Energy Minister in charge of smart metering, to ask about the cost benefits of smart meters. She told me that customers should see a reduction in their bills of around £26 by 2020 due to smart meters. That is just 1.5 per cent saving for the average user.

The programme is costing £10.9bn over five years for 30 million customers, which represents a cost per customer (that we will pay) of £360 - to save £26! Where is the economic sense in that?

John Spiller CEng FIET
By email

British sea power

The British Isles are surrounded by tidal water and contain many rivers and estuaries. The power contained in these waters and their large volumes constantly moving each hour of the day represents more energy than all the nuclear power stations and wind farms in the country.

Why are we not harnessing this free energy with, for example, coastal turbines with reversible blades as the tides change?

We have all seen windmill generators stationary for lack of wind, while the tidal currents never stop moving. Are we wearing blinkers as all this free green energy goes to waste?

I have been retired as an engineer for many years, but there must be some forward-thinking engineers who will take up this challenge. If so, no longer will this country be held to ransom by imported power when we have this endless supply in our country. Entrepreneurial engineers please take up this vital and worthwhile work.

Bernard W Hancock CEng MIET
By email

Hydrophonics in action

With reference to Mark Everson’s letter about the potential for hydroponics to be used as a carbon-reduction measure (Letters, June 2014), I can assure him that the idea he has proposed is indeed realistic, and has been in use for some years here on the Isle of Wight, and no doubt in other areas also.

Not far from where I live there is an enormous salad-crop production facility under glass and using hydroponics. They use gas turbines to produce large quantities of warm CO2-laden gas, which is circulated through the glasshouses to assist the crops’ development. As a spin-off (to them) the turbines drive generators, which provide power for the facility and also for export to the National Grid.

EurIng Howard C Burford CEng MIET
By email

Keeping track of aircraft

Following the discussion about aircraft tracking in the wake of MH370, it seems to me that the key requirement is for continuous satellite pinging of GPS position with global coverage, combined with a ground-based correlation system, which compares position with flight plan and raises alarms in the event of loss of ping or significant deviation from plan. Even if the pinger can be turned off by the crew, in the MH370 situation that would have alerted the authorities and triggered an immediate response.

It should be possible to give the satellite antenna installation an autonomous mode so it falls back on an internal battery and GPS receiver to ping even if cut off from power and avionics sensors. This should represent a negligible risk especially if the entire unit were contained in a fireproof housing. Battery power could be conserved by an adaptive ping that would report less frequently when the aircraft vector is constant.

I am rather astonished that such a ‘ping and correlate’ system was not mandated as part of the response to 9/11. It would provide significant assistance and early warning in the event of terrorist incidents as well as accidents that the aircrew cannot report for any reason. Such a system could also be the basis of an effective cross-check on ATC radar systems and even a comprehensive warning system both for potential aircraft to aircraft and aircraft to ground collisions.

John Hind CEng MIET
By email

Vacuum cleaner mystery

Why is the efficiency of domestic vacuum cleaners so low? The question arises from my retirement research project, the Coanda disk aircraft (www.coanda.co.uk), which is intended as a small unmanned aerial vehicle for urban area use.

This has involved studying fluid dynamics, a new field to me. The Coanda disk aircraft uses a turbine-like fan similar to the type commonly used in ordinary domestic vacuum cleaners but required to deliver induced air power of the order of 70W for an all up vehicle weight of about 2kg.

To understand the problems of designing a power unit I have investigated the vacuum cleaner and found that whereas the input electrical power might be of the order of 1kW; the induced air power at the business end is typically less than 0.5W.

Bob Collins
Wimborne Minster, Dorset

Careful with that drone

I’m sure I wasn’t the only reader to notice the item in your June 2014 Software Reviews about the Parrot AR.Freeflight package and associated AR.Drone hardware. Most of us must have seen these fascinating devices or similar on YouTube. Most readers will probably have enough engineering experience to wonder what fascinating failure modes these low-price systems can exhibit.

Fortunately for us in the UK at least, the boffins at the Civil Aviation Authority have applied their minds to the matter and have included what they consider to be appropriate regulations into UK air law under the topic heading ‘unmanned aerial systems’. The law gets most strict when the devices are used in the vicinity of buildings and/or people, and stricter still if they are used for financial gain. Fortunately they have also provided guidance in a form which is eminently readable to anybody used to handling regulatory material of the sort that so many of us use in our daily working lives (see tinyurl.com/8mtksm8).

What’s this got to do with us? The CAA have been known to prosecute and the courts have already convicted.

Joan Walsh JP CEng MIET
By email

I was disappointed that in his review of the Parrot AR.Freeflight app in the June issue, Bryan Betts did not mention that there are legal restrictions governing the use of unmanned aircraft/drones in built-up areas. These devices are subject to UK aviation law and as such cannot be flown within 150m of a congested area - the photo of a row of houses used in the review almost certainly breaches this law.

We certainly do not want to spoil the fun of recreational users of unmanned aircraft, but these laws are in place solely to protect members of the public. The Parrot AR. Drone 2.0 weighs almost 2kg and is clearly a safety risk to anyone standing below it should it suffer a systems failure, collision or its operator simply losses control. Users of unmanned aircraft need to take responsibility for each flight, and that includes understanding where they are allowed to fly their devices. More information is available at www.caa.co.uk/uas.

Gerry Corbett
Unmanned Aircraft Programme Lead, Civil Aviation Authority

Living with electric vehicles

I would like to draw attention to really good example of consumers working with manufacturers and distribution network operators to understand how electric vehicles will affect our demand profiles and technology to manage their demand.

My Electric Avenue (myelectricavenue.info) has demonstrated that consumers do care and want to be involved in developing innovation. It is also an excellent way to enthuse the next generation of engineers.

Dr Mary Gillie CEng
Chester

Socket cautionary tales

Recently I had to replace several 13A sockets in a newly purchased residence because they offered undue resistance to the insertion of standard 13A plugs. One of these sockets had a broken neutral contact. Investigation showed that a previous occupant had used plastic socket covers in the belief that they would guard against accidents to children.

I wholeheartedly endorse the letter from Peter Munro in your May 2014 issue. The general public are largely unaware that BS1363 socket outlets have built-in safety shutters. They are also unaware that the widely available ‘safety’ covers are potentially dangerous and do not have to conform to any established safety standards.

I pointed out the dangers to a national accident-prevention organisation and suggested that stricter regulation should be introduced. The reply was that while they do not recommend the use of such devices, “there is considerable merit in the use of socket covers as part of wider efforts by new parents to recognise and respond to everyday domestic hazards”.

The same reply contained the incredible statement that, “Whilst it is conceivable that poor design of socket covers might cause damage and shorting within electrical sockets, this is more likely to be the result of wear and tear using ordinary 13A plugs with their hard metal contacts rather than plastic socket covers”.

David G Buckley C Eng MIET
Milton Keynes

South Africa socket

In April this year, South Africa adopted a new standard for socket outlets based on IEC 906. For decades, South Africa has used a 15A round pin design, which was abandoned in the UK when the 13A rectangular pin design was adopted.

Because of how the sockets are recessed, it is impossible to touch the pins when putting in or taking out a plug. This is regarded as the safest design available. Yes, the shutters over the live and neutral sockets can be opened by inserting something into the earth socket; there’s no practical way to prevent this. But the compact design will make it impossible to design socket covers which can be used to do this.

It has one other great advantage: the compactness means that multiple sockets can be installed in one conduit box, making it easier to avoid the sort of electrical spider’s webs that adorn many offices and kitchens.

Mike Young
Sedgefield, South Africa

Socket and key

The letter about the danger of socket covers reminded me of a scary incident with my son, 30-plus years ago, when he was a baby. One evening, when my wife and I were watching television, he climbed out of his cot and over the top stair gate, came down the stairs, climbed over the bottom stair gate, climbed onto a stool onto the kitchen bench, opened my wife’s handbag, removed her set of keys, used a key to lever a socket cover out, inserted a key into the earth socket (thus opening the live and neutral) and inserted another key into the live socket.

Simultaneously there was a scream from the hallway, the television went off and the lights went out. Obviously we feared the worst but his only injury was a small burn on his hand from the molten key. In those days we had an Austin A35 car having a metal key with no plastic moulding. The car key in the earth socket, the metal key ring and the metal front door key in the live socket provided a continuous conductor from live to earth. I dread to think what the outcome would have been if the car key had been a modern one with a plastic moulding!

Norman Burrow CEng FIET
By email

On the shelf

I came across a depressing sight in Heffers bookshop in Cambridge recently. Pictured above right is the sole contents of books on electronics, electrical engineering and telecommunications. The principal bookshop for Cambridge University and this is all they can muster. Despite the fact there are hundreds of job vacancies for electronics engineers in Cambridge, that’s all they have - one meagre shelf. Incidentally the shelf space given over to psychology, English literature and the bewildering array of other degree subjects that will not lead to one single manufacturing job is staggering.

Allen Brown MIET
Cambridge

Lunch break project

Recent letters in E&T made me recall my apprentice days some 75 years ago, when I made a battery charger during my lunch breaks. It consisted of metal plate rectifier, a transformer with various tappings on secondary winding for voltage control, rotary switch, meter etc. Power supply was by twin lighting flex and lampholder adapter. The lamp holder was concealed within a wooden case, made by the firm’s chippy during his lunch break.

JW Main MIET
Hook, Hants

Why bother with DSLR?

John Billingsley (Letters, June 2014) gives a misleading account of why ‘real’ photographers use DSLR cameras. As a chartered engineer and an amateur photographer I believe that it should be better understood that photography is a combination of art and science, the scientific relevance being greater than ever since the introduction of digital image capture.

The nature, location, lighting and size of a successful image mean that it is impossible to cover the full range with a single lens. This then leads to the necessity of a camera with an interchangeable lens system, hence the development of film SLR cameras.

The advent of digital technology allowed the manufacture of small compact cameras and the incorporation of cameras into mobile phones, but with severe limitations. The absence of a viewfinder presents real problems in bright outdoor situations and while modern electronics allow control of white balance, ISO (the equivalent of film speed) and dynamic range along with many other features, these are not readily incorporated in either mobile phones or small compact cameras.

Finally there is the matter of the image sensor device. Ideally this should be physically large to allow for a large number of pixels, which are relatively large. The former to provide high-definition and the latter to give lower noise output, which necessitates a full-frame DSLR.

Taking all of the above into consideration, it would appear obvious that the DSLR camera must be the first choice for anyone with a serious interest in photography.

Geoffrey H Robinson CEng FIEE FIET
St Andrews

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